The invention relates to a sensor system that enables the position of a vehicle occupant located in a vehicle to be determined relative to that vehicle. For this purpose, distance sensors are used which can sense the relative position of a vehicle occupant.
Most passenger cars today are equipped with so-called airbags. These inflatable airbags are currently triggered almost exclusively when a predefined acceleration or deceleration, usually measured on the vehicle, is exceeded. In this process it is not determined whether or not, for example, the vehicle occupant is located directly in front of the airbag or whether or not a seat in the vehicle is occupied. Furthermore, it is not possible to detect what type of occupant is in the seat, for example, whether the seat is occupied by a child, an adult or, a baby carrier. The airbag may thus be triggered even when the airbag is not necessary to protect anyone against injury. However, on the other hand, triggering of the airbag when the seat is not occupied in a usual way can lead to injury from the triggering of the airbag. An unusual occupation of the seat occurs, for example, if the vehicle occupant is located very close to the windscreen at a particular moment or also if a small child is located on the front passenger seat.
The situation occurring on a vehicle seat can be detected, for example, by visually sensing the vehicle occupant and by using image processing. The type of seat occupation and the position of the vehicle occupant, in particular of the front seat passenger, can thus be determined. With this visual sensing, it is necessary to record three-dimensional images and to operate completely independently of the ambient illumination. Such a system is enhanced by using a CMOS camera with three-dimensional resolution and with appropriate infrared laser illumination. This in turn results in problems in terms of the acceptance of the laser illumination. Furthermore, such optical systems are relatively complex and cost-intensive because of the required highly integrated chips, processors for the image processing, laser illumination with power electronics, and the appropriate optics. In addition, covering or soiling can severely disrupt optical systems.
It is accordingly an object of the invention to provide a sensor system and a method for determining the position of vehicle occupants in a vehicle which overcomes the above-mentioned mentioned disadvantageous of the prior art apparatus and methods of this general type. In particular, it is an object of the invention to provide such a sensor system that is immune to interference and that can be implemented in a cost-effective manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, a sensor system for determining a position of an occupant in a vehicle. The sensor system includes a configuration having at least one elongated electrical conductor for generating at least one magnetic field that decreases in a direction transverse to the at least one electrical conductor. The sensor system includes at least one magnetic field sensor for detecting a strength of the at least one magnetic field in order to determine a distance between the at least one magnetic field sensor and the at least one elongated electrical conductor. A seatbelt has a portion configured to lie against a chest region of a vehicle occupant. The portion of the seatbelt includes one of the at least one elongated electrical conductor and the at least one magnetic field sensor. The other one of the at least one elongated electrical conductor and the at least one magnetic field sensor are configured at, at least one predetermined point in a vehicle such that a position of the vehicle occupant can be determined from a detectable relative position of the seatbelt.
With the foregoing and other objects in view there is also provided, in accordance with the invention, a method for determining information regarding an occupant in a vehicle. The method includes steps of: providing a configuration including at least one elongated electrical conductor for generating at least one magnetic field that decreases in a direction transverse to the at least one electrical conductor; providing at least one magnetic field sensor; providing a seatbelt having a portion configured to lie against a chest region of a vehicle occupant; configuring one of the at least one elongated electrical conductor and the at least one magnetic field sensor in the portion of the seatbelt; configuring the other one of the at least one elongated electrical conductor and the at least one magnetic field sensor in at least one predetermined point in a vehicle; detecting a strength of the at least one magnetic field to determine a distance between the at least one magnetic field sensor and the at least one elongated electrical conductor; and determining a position of the vehicle occupant from the distance between the at least one magnetic field sensor and the at least one elongated electrical conductor.
Hitherto there has been no differentiated triggering of an airbag in a vehicle, i.e. use has not been made of triggering conditions which provide more detailed information on the respective vehicle occupants. The inventive system first attempts to determine the position of vehicle occupants, and possibly also determines the type of seat occupation. The inventive system uses the seatbelt to obtain a reference position for a vehicle occupant on a specific seat to provide a simple, robust, and cost-effective sensor system which can sense both the position of the vehicle occupant relative to an airbag and the type of seat occupation. To do this, an elongated electrical conductor for generating a magnetic field is mounted in the portion of the seatbelt which rests against the chest region of a vehicle occupant. Various types of shaped coils (air-cored coils) woven into the belt are also conceivable. These magnetic field-generating units are preferably supplied with alternating current from one end of the seatbelt. The magnetic field, which decreases with increasing radius defined perpendicularly with respect to the longitudinal extent of the belt or the coil axis, can be detected by induction coils for example. The distance dA of a vehicle occupant away from the dashboard can therefore be detected by an induction coil using its output voltage UA. This is due to the fact that a magnetic field H which is generated in the seatbelt by an electrical conductor decreases transversely with respect to its longitudinal extent as the radius increases, in accordance with the equation H=I/2 xcfx80r, where I is the current. The field strength detected using the induction coil is a measure of the distance between the induction coil and seatbelt or electrical conductor. The distance ds between the seatbelt and an induction coil mounted to the rear of the vehicle occupant in the backrest can also be determined. In particular, this system can determine the type of seat occupation using the measured distance ds. The type of seat occupation can be differentiated, for example, into large or small person, heavy or lightweight person etc.
Although the invention is illustrated and described herein as embodied in a sensor system for determining the position of vehicle occupants in vehicles, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.